MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) is a side product of meperidine synthesis. When given to man and primates it induces persistant symptoms of parkinsonism and the clinical signs can be reversed by administering L-DOPA or bromocriptine. In rhesus monkey, MPTP induces degeneration of the nigrostriatal pathway with a concomitant reduction of dopamine. Our objective was to determine if similar degenerative changes of dopaminergic neurons could be induced in mice and to determine if the acetylcholine content of cholinergic neurons might be altered by the loss of dopaminergic neurons.